Synchrotron and laboratory X-ray CT in natural and cultural heritage

X-ray micro-Computed Tomography has become a very common technique used in all fields of science. Developed first for medical purposes, the non-destructive aspect was of particular interest for many types of industries as it could allow inspection of product and prevent (or understand) failure. Medical X-ray CT apart, Engineering and Material Sciences are the predominant users of this technique, either in industry or academia. However, the user community in other academic groups has significantly grown over the few decades, building cases to purchase instruments in geology or biological departments and even in natural and cultural heritage museums. The latter community is quite peculiar in the world of X-ray CT: samples are of all sorts of sizes, shapes, and density and unlike the engineering world, it is usually unthinkable to alter the object or sample to facilitate the tomographic experiment. Worse still, some objects can only be oriented in a special way, or may only be handled by specific people with special training. Yet, the discoveries in the natural and cultural heritage fields are astonishing, solving decades-long mysteries and offering new ways to study museum collections. Fossils and art objects are also commonly taken to synchrotron facilities. These large particle accelerators are the crème de la crème when it comes to X-ray tomography: the incomparable flux, the parallel beam, the coherence, are all specifications in which a synchrotron emitted X-ray beam excels. Far from being anecdotal, these fields are now included in the upgrade roadmap of these facilities, as shown by current construction of the BM18 beamline at the European Synchrotron Radiation Facility which is built to accommodate specific requests from the natural sciences and cultural heritage community.